1. Field of the Invention
This invention relates to automated guideway transit (AGT) systems and, more particularly, to an auxiliary drive traction system for use with AGT vehicles.
2. The Prior Art
Automated guideway transit (AGT) systems are becoming a popular, efficient, and environmentally clean method of mass transportation, and are potentially a significant factor in energy conservation. In general, the drive systems for AGT vehicles comprise a motor located within the AGT vehicle which provides power to rotate the drive wheels. The drive wheels extend beneath the AGT vehicle body, resting upon a generally flat track surface which serves as a drive wheel running surface.
In addition to the main drive wheels many AGT vehicles have lateral guide wheels which are positioned on a separate guide wheel running surface that may be perpendicular to the drive wheel running surface. The guide wheels are designed to provide directional stability to the AGT vehicle as it travels along the guideway assembly. Typically, the guide wheels are freely rotatable, having no relationship to the power drive system of the AGT vehicle.
When AGT systems are used in cold weather climates, the drive wheel and guide wheel running surfaces of the tracks are exposed to the weather and can experience buildups of ice and snow. Even the formation of dew or frost on these running surfaces increases the hazard to passengers and may reduce the AGT system's operating efficiency. The collection of ice or snow on the AGT system's drive wheel and guide wheel running surfaces significantly reduces the AGT vehicle's traction. This problem is especially troublesome during the acceleration and deceleration phases of the AGT vehicle's operation. The lack of traction may be particularly hazardous in emergency situations.
Moreover, even during favorable weather conditions, if power to the main drive system is interrupted, the AGT vehicle becomes completely inoperative. Thus, power failures or mechanical breakdowns in the AGT vehicle's main drive system may seriously interrupt the traffic flow of an AGT system for prolonged periods.
What is needed is an auxiliary drive traction system to help provide good traction even when the normal drive wheel running surfaces are covered with snow and ice, and to provide means for operating the AGT vehicle in the event the main drive system becomes inoperable.